10 BULLETIN 283, U. S. DEPARTMENT OF AGRICULTURE. 
tivity in the apparatus. Moreover, the constant impinging of the 
gases on the walls of the spiral flue, which can be cooled either by 
air or water, makes it practicable to maimtain the gases at a temper- 
ature most favorable for the efficient yield of sulphuric acid. 
In the following laboratory experiments, however, the sulphur 
dioxide (SO,) used was not directly derived from burning pyrites or 
sulphur, so it was necessary to heat the system artificially to at- 
tain a temperature as high as that obtamed under factory conditions. 
The sulphur dioxide was obtained from a small cylinder of the 
liquefied gas, which was weighed both before and after each experi- 
ment, and the SO, used thus determined. The oxides of nitrogen 
(chiefly N,O, and N,O,) were produced by the action of dilute nitric 
acid on copper, and the rate at which they were used was roughly 
50 se 
Ar and Stearn )) 
Fic. 1.—Apparatus used in proposed new method for manufacture of sulphuric acid. 
determined by allowing the gases to bubble through dilute sulphuric 
acid saturated with these gases. A mixture of air and water vapor 
was obtained by drawing air through a flask of water heated to the 
boiling point. 
The apparatus employed (fig. 1) consisted, first, of a large test 
tube (A), having a capacity of 200 ¢.c., and containing a little water 
heated to boiling. The oxides of nitrogen, sulphur dioxide, air, and 
water vapor were led to the bottom of this vessel by separate tubes 
and given a preliminary mixing. From the test tube the gases were 
drawn into the lead or glass spiral (B), which was heated to about 
90° C. in order to facilitate the reactions. In wmding downward 
through this spiral the warm gases were thoroughly mixed, with the 
result that most of the sulphuric acid produced in the system was 
formed in this coil. The residual gases were then passed through 
